1. Field of the Invention.
This invention relates to holographic multicolor optical elements for use as multicolor filters in liquid crystal displays and methods of making the elements.
2. Description of Related Art.
Multicolor liquid crystal display (LCD) assemblies have many uses including displays in vehicle dashboards, watches, calculators, televisions, computers, video camera view finders, etc. Conventional multicolor LCD assemblies are adapted to display images by transmitting light of different colors, typically red, green or blue, through selected miniature areas of a surface called pixels. Illustrative multicolor LCD assemblies are disclosed in U.S. Pat. Nos. 4,834,508, 4,878,741, 4,929,060, 4,966,441, 5,089,905, 5,113,274, 5,130,826, 5,150,236 and 5,245,449.
Conventional multicolor LCD assemblies typically use absorptive filters to absorb light except the desired color to be transmitted through each pixel. Illustrative absorptive filters for use in multicolor LCD assemblies are disclosed in U.S. Pat. Nos. 4,822,718, 4,876,165, 4,966,441, 5,185,059, 5,229,039, and 5,232,634 and in Japanese patent publications JP-04355451, JP-05313009-A and JP-05343631. In certain instances, as in U.S. Pat. No. 4,229,039, the color filter material has a dual role and also functions as an orientation layer in addition to a color filter.
The absorptive filters rely on a high concentration of particular dyes to insure sufficient absorption of background light and unwanted light of two colors out of the red, green and blue colors. The absorptive dyes typically absorb broad bands of light which restricts the colors, shades and resolution of the display. Further, the absorptive dyes are frequently not highest in transmission at the desired wavelength. Large absorptive filters are difficult to manufacture with high quality especially when pixel size is small throughout the filter. It is also desirable to find a lighter weight alternative to conventional absorptive filters.
Conventional LCD color filters typically also employ an opaque mask which creates a border, known as a "black matrix", surrounding each pixel. The black matrix is typically produced by sputtering chrome onto the glass substrate, applying photoresist, patternwise imaging the photoresist, etching the chrome and stripping the photoresist. It would be desirable to create the black matrix simultaneously with the creation of the color filter elements, thus simplifying the manufacturing process by reducing the number of manufacturing steps.